Flexible and lightweight supercapacitors with superior mechanical flexibility and outstanding capacity are regarded as an ideal power source for wearable electronic devices. Meanwhile, incorporating additional novel characters such as transparency and electrochromism can further benefit the development of smart supercapacitors. Nevertheless, the application of the commonly used planar‐structural current collectors is seriously restricted by their intrinsic properties such as poor rigidity, large thickness, and limited loading surface area. Flexible and ultralight current collectors with 3D architecture, high conductivity, and easy integration are believed to be the most appropriate alternatives to build high‐performance supercapacitors. In this study, a novel and scalable manufacturing technique is developed to produce a flexible and ultralight 3D Ni micromesh (3D NM) current collector for supercapacitor. Flexible smart supercapacitor integrated by 3D NM and high active Ni–Co bimetallic hydroxide (3D NM@NiCo BH) delivers a considerable rate performance (60.6% capacity retention from 1 to 50 mA cm−2). Furthermore, the fabricated hybrid supercapacitor device integrated with electrochromic functionality can visually indicate the energy level by a color display. This flexible electrochromic supercapacitor based on ultralight 3D Ni micromesh provides a novel insight into multifunctional energy storage systems for smart wearable electronic devices.
M-type barium hexagonal ferrite films with the crystallographic c axis out of plane were successfully deposited onto a Pt template using a metallo-organic decomposition technique. For the best film, x-ray diffraction patterns revealed strong (00l) reflections and a texture fraction of 0.953, confirming the out of plane c axis orientation. Atomic force microscopy images confirm hexagonal grains in this film with an average lateral size of ∼500 nm. Hysteresis loops revealed a high effective out of plane anisotropy field, high perpendicular remanent magnetization Mr=0.93 Ms, and out of plane coercivity of 4.5 kOe. Out of plane Ferromagnetic Resonance measurements determined the values of γ=2.79 GHz/kOe and effective anisotropy field. The full width at half maximum FMR linewidth was 338 Oe at 60 GHz. These properties are suitable for possible use in on-wafer millimeter wave devices.
We developed the thin film microwave magnetic material, M-type barium hexagonal ferrite (BaM) doped with Al, for signal processing devices operating above 40 GHz with little to no applied magnetic field. Al was chosen as the dopant material because it significantly increases the already strong anisotropy field of BaM. A series of thin film BaAlxFe12-xO19 samples, x ranging from 0 to 2 in 0.25 steps, were deposited on Pt templates using a metal-organic decomposition growth technique. The resulting films are polycrystalline and highly textured, with the hexagonal c-axis directed out of plane. These films are also self-biasing; easy axis hysteresis loops have a high squareness ratio, s, in the 0.83-0.92 range. As expected, the anisotropy field increases with x, ranging from 1.34 to 2.19 × 106 A/m (16.9-27.5 kOe) for x = 0-2, while the saturation magnetization Ms decreases with x, ranging from 0.334 to 0.175 × 106 A/m (4πMs = 4.2-2.2 kG) for x = 0-2. These values were measured at room temperature, but the temperature dependence of these quantities was also measured below room temperature, down to 30 K. The measured ferromagnetic resonance linewidths, on the order of 12-30 × 103 A/m (140–370 Oe) for compositions below x = 1, indicate device-quality films. Above a certain threshold, the linewidth increases linearly with frequency at a rate of 0.2-0.64 × 103 (A/m)/GHz (2.5-8 Oe/GHz) for x = 0–1, respectively. The behavior of the linewidth is correlated with the structural properties of the films measured using x-ray diffraction and atomic force microscopy. The results of magnetic force microscopy, Curie point measurements, spectral ellipsometry (index of refraction), and magneto-optical measurements are also included and discussed.
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